I think the thing I'm hating most about this page... Is the fact I have to wait until Tuesday to find out the answer. -Scoots to the edge of the seat- Gotta love comics that have you anticipating the next update XD

I figure the ability to 'see' functions in the same way as some De Lint novels. I'm thinking The Blue Girl specifically. The the book the main character, Imogene is exposed to the world of the Fey in that she sees Adrian (ghost) who tries to open her mind to the abandoned house spirits/ brownies in the school but she resists. Then Pelly (imaginary friend from childhood) comes back and through long time exposure (dreams into reality for this book) opens her mind to seeing other things. Eventually her accepting that they do exist put her in danger.
I figure that Kay was able to see P as a child because her world boundaries were more flexible and thus she was more open to being able to see him, in contrast with her parents who are shown as having seriously strict boundaries. However, rather than wholeheartedly accepting the existence of Fey (as I am assuming the people she's seeing now are) she accepted P as an anomaly. Her exposure, however has gone up recently and thus her awareness has also increased, as seen in the increasing frequency of her observing Fey individuals. My theory here is that the sudden increase can be attributed to her interactions with Juan ,who bares a striking resemblance to the dog seen Issue 1 page 10 and 11, and is later seen sniffing the air when P is around, and has pronounced canine. This could also explain why P was so adamant in his disapproval of said suitor.
There are three reasons P could be afraid of Kay being exposed to the world of the Fey so quickly, if at all. This, of course, also follows the logic of De Lint. In The Blue Girl the school brownies, and again in a short story through Oak's daughter states that to show an individual their world too quickly can cause a person to go into a sort of shock in which they block out that world and loose all memory of people from it. P could have been trying to protect her in this way and delayed telling her until it was too late (meaning her definitions of reality were seemingly concrete). This delay could have been caused by him seeing Kay face so much conflict from interaction with him, I mean think of what she'd have gone through if she could see a whole world. Besides, lore is littered with tales of children being tricked by Fey and even taken. The second reason could be that he was afraid for Kay's safety, the Fey while often seeming harmless can be very dangerous, especially to a human girl. The third reason is again from another DeLint short story. If one tries to force belief in something, they loose said belief entirely and thus loose touch with whatever they believe in (this is from a story in which said beliefs are embodied by birds that will literally fly away)

Now obviously I'm not going to comment if you are right or wrong - (you'll just have to keep reading! XD)but I just wanted to say I really appreciate your thoughtful comment and that you are thinking so much into the story. It makes me happy to see people getting invested in the world. ^^